1. Field of the Invention
The present invention relates to an injection mold apparatus for manufacturing a resin injection molded article, and more particularly, to an injection mold apparatus having a heating means and a cooling means in the mold apparatus to heat or cool a mold during the injection process.
2. Description of the Related Art
Injection mold is a typical method of molding a synthetic resin such as plastic or the like. For such an injection mold, molten resin is injected and filled into a cavity of the mold formed in a certain shape and then cooled and hardened to mold a product having the same shape as the cavity.
In general, a surface of the injection molded product is roughly formed and thus an additional painting or surface treatment process is required, and accordingly, the process becomes complicated.
Consequently, in order to smoothen the molded surface and simplify the process, a cold mold in which injection molding is carried out and then only an outer portion of the mold is cooled down but an inner portion thereof is slowly cooled down has been developed. In this case, thermal strength can be enhanced, but the inner portion is in a low-temperature state at the initial stage even when a high-temperature mold compound is injected and thus it is difficult to maintain the temperature, thereby causing difficulty in smoothening the surface of the injection molded product.
Accordingly, molding technologies in which injection is carried out while maintaining the mold at a high temperature and then the mold is rapidly cooled down have been studied, and as a result a high-temperature mold technology has been developed. In the high-temperature mold technology, the temperature of the mold is maintained at a high temperature by a hot wire or the like embedded in the mold to perform injection and thus resin is uniformly filled into the cavity. Furthermore, rapid cooling is uniformly carried out through a coolant passage embedded in the mold. As a result, the surface of the molded article is uniformly formed to allow the formation of a smoothened appearance. Furthermore, an additional surface treatment process is not required, thereby allowing the simplification of the process through no-painting.
In such a high-temperature mold technology, the process of increasing the mold temperature and decreasing the mold temperature becomes a key factor for determining. the surface state of the injection molded article. For the technology of decreasing the mold temperature, a cooling plate is provided at a rear surface of the cavity mold plate having a heating means, and the cooling plate is brought into contact with the cavity mold plate during the cooling process, thereby performing rapid cooling.
Here, the cooling plate should be uniformly brought into contact with the cavity mold plate to enhance the cooling efficiency and reduce the cooling temperature variation, thereby improving the surface state of the injection molded article. However, the cavity mold plate is rapidly cooled down in a high-temperature state, and therefore thermal expansion and deformation occurs in a mass production system requiring frequent use. As a result, the cavity mold plate and the cooling plate are not uniformly brought into contact with each other, thereby causing a problem of severe cooling temperature variation.